Today’s android devices are probably more powerful than your PC. And while 2D games look simple, if you’re doing them in an engine that’s not designed specifically for that purpose then it’s not going to run as well as it could. UE4 is designed for intense 3D graphics, while it can do some 2D, that’s just a bonus and not a primary purpose of the engine. If they try to support old technology then it means they can’t improve certain features.